The present invention relates to a material feed apparatus for the feed of material between a material supply location and a delivery location and, more particularly, to a material feed apparatus for use with fossil fuel delivery systems including the coal piping for delivering pulverized coal to coal fired steam generators.
Coal fired furnaces are typically provided with a plurality of ducts or pipes through which pulverized coal and air is directed to a plurality of fuel-air admission assemblies arrayed in respective vertically extending windboxes. The windboxes are disposed in one or more walls of the furnace and each introduces coal and air into the furnace.
Pulverized coal firing is favored over other methods of burning coal because pulverized coal burns like gas and, therefore, fires are easily lighted and controlled. Such systems may include one or more pulverizers, also referred to as mills, that are used to grind or comminute the fuel or, alternatively, may not include any pulverizer because a supply of pulverized coal available.
The pipes directing the coal to the respective windboxes are large and cumbersome. Typically the pipes are provided with large couplings or bolted flanges to couple the end abutting axially adjacent portions together. The normal nozzle assembly requires regular maintenance because the pulverized coal has a severe erosive effect. A typical pulverizer will move between 7 and 50 tons of coal every hour. The coal typically moves at a velocity of 75-90 feet per second within the fuel transport pipe.
A typical coal distribution system includes a number of distributors intended to split the flow of air and pulverized coal into two discrete pipes. It is desired that the distributors take the homogeneous mixture and deliver identical quantities of that homogeneous flow to each of the two discrete pipes. Each of these distributors is a Y-shaped duct. Each of these Y-shaped ducts has an inlet and two outlets. U.S. Pat. No. 5,934,205 to Gordon et al discloses a Y-shaped distributor body and a splitter disposed in the distributor body for dividing a flow of pulverized coal between first and second outlets.
In connection with the feed of pulverized coal to the feed burner nozzles of a combustion chamber. U.S. Pat. No. 6,055,914 to Wark notes that an exhauster fan first throws the coal radially into a primary discharge chute and that the flow of coal/air leaving the exhauster fan is uneven, whereby the coal/air flow to the burners tends to be light on one side or wall of the chute and heavy on the other side or wall of the chute in terms of both particle size and distribution.
U.S. Pat. No. 6,055,914 to Wark describes a prior art solution which involves providing xe2x80x9criffle boxesxe2x80x9d in the chute between the fan and the burners. A riffle box is a series of vertical, spaced plates separated by angled separator bars with alternating orientation from plate to plate and notes that, in accordance with one theory, it is believed that the separator bars on one plate will deflect the coal in one direction, while the separator bars on adjacent plates will deflect the coal in the opposite direction, thereby splitting and redistributing the flow for a more homogeneous mixture. It is further noted in this reference that the typical arrangement is to provide a series of riffle boxes, with a first riffle box splitting the flow like a xe2x80x9cYxe2x80x9d into two chute branches, and a subsequent riffle box on each of the first two branches splitting the flow again into a total of four chutes. Each chute typically fuels one of four corner-mounted burners in a tangentially-fired combustion chamber.
U.S. Pat. No. 6,055,914 to Wark notes that the riffle boxes have proven ineffective in providing a more homogeneous mixture to the burners, and the coal/air flow reaching the four combustion chamber burners differs significantly from burner to burner. The reference cites several problems which result from a riffle box arrangement: too lean a mixture at a burner can create NOX: oversized particles and inefficient burning create LOI (loss on ignition) contamination of the ash byproduct and reduced combustion efficiency: and, perhaps most importantly, the out-of-balance burner flow distorts the combustion chamber fireball from the ideal spherical shape to an undesirable elliptical shape, creating hot and cold spots in the boiler tubes and causing gas control problems.
It is an object of the present invention to provide a moving fluid distributor apparatus which will be more durable.
Another object of the invention is to provide an apparatus for feeding material between a material supply location and a delivery location which permits more precise and reliable control of the distribution of the material between two or more branch feed paths.
A further object of the present invention is to provide an apparatus for feeding material between a material supply location and a delivery location which distributes material between two or more branch feed paths in a manner which minimizes any loss of pressure.
An additional object of the present invention is to provide an apparatus for feeding material between a material supply location and a delivery location which distributes a mixture comprised of a fluid transport material and a solid material between two or more branch feed paths in a manner in which the distribution of the fluid transport material between the branch feed paths remains substantially the same following a re-distribution of the entrained solid material between the branch paths.
In accordance with one aspect of the present invention, it has now been found that these and other objects of the invention may be attained in an apparatus for influencing the travel properties of a material moving between a material supply source and a delivery location which includes means forming a feed path along which material travels as the material is enroute from the material supply source to the delivery location and means for moving at least one of the upstream passage periphery and the one branch entry relative to a reference axis. In accordance with further details of the one aspect of the present invention, the feed path passes through an upstream passage bounded by an upstream passage periphery each point of which is at a predetermined radial spacing from the reference axis and the feed path including one branch having a branch entry downstream of the upstream passage and another branch having a branch entry downstream of the upstream passage. The stream of material travels through the upstream passage thereafter separating into at least two portions with one portion of the material entering the one branch through its branch entry and thereafter traveling along the one branch and another portion of the material entering the another branch through its branch entry and thereafter traveling along the another branch in a manner in which the another portion of the material and the one portion of the material are segregated from one another during their respective travel along the one branch and the another branch. Also, the means for moving at least one of the upstream passage periphery and the one branch entry relative to the reference axis moves the at least one of the upstream passage periphery and the one branch entry relative to the reference axis such that the one portion of the material and the another portion of the material, prior to their respective segregated travel along the one branch and the another branch, are comprised in unseparated manner in the stream of material as it travels through the upstream passage and the portions of the material thereafter travel in segregated manner in their respective branches with the travel properties of the one portion of the material in the one branch being different than its travel properties before the movement of the at least one of the upstream passage periphery and the one branch entry relative to the reference axis.
According to another aspect of the present invention, the material feed apparatus is configured for cooperation with an associated furnace having the capability of burning coal which is delivered thereto as a mixture of pulverized coal and air.